Television signal distribution systems typically broadcast television signals to individual users or subscribers on a plurality of individual television channels. The channels may be modulated onto one or more carrier frequencies within a discernable frequency band. Some wireless television signal distribution systems use one or more geosynchronous satellites to broadcast a broadband television signal to receiver units within a large geographic area, while other wireless systems are land-based, using one or more transmitters located within smaller geographic areas to broadcast to individual receiver units within those geographic areas.
The receiver unit receives and processes transmitted waveforms. The receiver unit in a satellite systems typically includes a satellite dish connected by a cable to an integrated receiver/decoder unit (IRD). The satellite dish is aimed toward the satellite, and the IRD is connected to the user's television in a similar fashion to a conventional cable-TV decoder.
Along with the audio and video signals associated with the television channels, the satellite transmits various files such as text and graphics. These files and portions of these files may be used by the IRD to provide the user with additional information such as supplements to an electronic program guide. For example, a file may describe a particular actor or identify a movie's director.
Typically, these files are stored in a relational database and retrieved by key fields. However, relational databases, particularly in an IRD environment, are slow and consume a large portion of RAM. Consequently, users must wait to retrieve program guide data and/or the cost of the IRD is increased by additional memory. Further, the names of the fields in the relational database (e.g., “director”) are typically fixed. New categories of information cannot be easily added after the IRD has been shipped.